Solutions of polymers of vinylidene cyanide in alkyl esters of phosphoric acid



Patented Apr. 29, 1952 UNITED STATES PATENT OFFICE SOLUTIONS OF POLYMERSF VINYLIDENE CYANIDE IN ALKYL ESTERSHOF PHOS- PHORIC ACID No Drawing.Application January 7, 1950, Serial No. 137,479

. 1 This invention relates to novel polymer S0111? tions and pertainsmore particularly to solutions of polymers of vinylidene cyanide inalkyl esters of phosphoric acid. 1 V

A copending application, Serial No. 11,336, filed February 26, 1948 nowU. S. Patent No. 2,589,294, .describes methods for the preparation ofhighly useful polymers .of vinylidene cyanide and discloses that'polyvinylidene cyanide of molecular weight in excess of 25,000 iscapable of being used to form excellent synthetic fibers, films andfilaments. However, only a very few solvents for this high molecularpolyvinylidene cyanide are known it being insoluble in almost all of thesolvents ordinarily employed in dissolving high polymers includingalcohols, carboxylic acids and their esters, ketones, hydrocarbons,chloro and nitro substituted hydrocarbons and the like.

Accordingly it is an object of this invention to provide a new class ofsolvents for polymers of vinylidene cyanide suitable for forming polymersolutions from which excellent filaments, films and the like may beprepared. Other objects will be apparent hereinafter.

It has now been discovered that the above and other objects are attainedby the use of alkyl esters of phosphoric acid as solvents forthepolymers of vinylidene cyanide. Polymer solutions are thereby obtainedwhich have the, desired viscosity for the spinning of filaments and thecasting of films. Moreover, the films and filaments prepared from suchsolutions possess many valuable properties including high tensilestrength and excellent resistance to the action of chemicals. The alkylphosphates are especially valuable solvents since they are economicallyobtained in large quantities and because they are readily soluble inwater, of low toxicitygand do not hydrolyze.

The esters of phosphoric acid which are useful solvents for polymers ofvinylidene cyanide possess the formula Rs-O wherein R1 is an alkylradical containing from 1 to 3 carbon atoms and each of R2 and R3 is amember of the class consisting of hydrogen and alkyl radicals containingfrom 1 to 3 carbon atoms. Included within this class of esters aremonoalkyl phosphates such as methyl phosphate,

phosphate, dipropyl. phosphate, methyl ethyl phosphate, methyl propylphosphate and ethyl propyl phosphate; and trialkyl phosphates such astrimethyl phosphate, triethyl phosphate, tripropyl phosphate, diethylmethyl phosphate, dipropyl ethyl phosphate and the like. The preferredalkyl phosphates for use as solvents for polymers of vinylidene cyanideare those which contain from 1 to 6 carbon atoms, especially trimethyland triethyl phosphate.

No special conditions or precautions are necessary: in preparing thepolymer solutions of this invention. Solutions may be made either byadding the polymer to the solvent or by reversing the order of addition.Solution of the polymer occurs at room temperature but is much morereadily efiected by heating the polymer-solvent mixture to a temperatureof about 50 C. to C.

It has been found desirable that the polymer solutions be stabilizedagainst possible polymer chain degradation if they are to be kept forappreciable lengths of time before use. Suitable stabilizers include theoxides of sulfur, and especially sulfur dioxide, as well as organic acidanhydrides. The use of a stabilizer is not a critical expedient however,for the solutions of vinylidene cyanide polymers in alkyl phosphatesremain relatively stable for a period of several days even when nostabilizing substance is present.

Solutions having any desired polymer concentration may be prepared sincethe solvent and the polymer seem to be miscible with one another in allproportions. However, solutions containing less than 30%, and especiallyfrom about 8% to 20% by weight of polymer are preferred for use asspinning or casting solutions.

The preparation of polymer solutions in accordance with the presentinvention as well as the use of such solutions in the spinning offilaments is more fully described in the following examples, whereinall'parts are by weight.

Example I 0.05 part of a fiber-forming polymer of vinylidene cyanide isadded to 0.35 part of triethyl phosphate. The mixture is gently warmedfor about five minutes whereupon a clear, syrupy, viscous solutionsuitable as a spinning solution is formed.

Example II Example I is repeated using trimethyl phosphate in place oftriethyl phosphate and a clear syrupy viscous solution suitable forspinning is again obtained.

Example III A spinning solution is prepared by dissolving 0.5 part ofpolyvinylidene cyanide of molecular weight considerably above 25,000 in4.0 parts of triethyl phosphate. To this solution 0.5 part of a mixtureof triethyl phosphate and sulfur dioxide (.168 part of sulfur dioxidefor each 1.406 part of triethyl phosphate) is added. The resultingsolution is water white and of a viscosity suitable for spinning. Thissolution is spun into a glycerin bath maintained at a temperature of 135C. to give a strong, lustrous filament.

Example IV A 12.5% solution is prepared by dissolving a fiber-formingvinylidene cyanide polymer in triethyl phosphate. The solution is spunat a rate of 44 inches per minute into a water bath maintained at 80 C.and wound onto a take-up bobbin at 2'76 inches per minute. The resultingfilament is quite useful as a textile fiber.

Example V 0.1 part of a polymer of vinylidene cyanide of a molecularweight considerably above 50,000 is dissolved in 14.06 parts of triethylphosphate which is heated to 70 C. The solution is of a viscositysuitable for spinning. After six days, the solution is less viscous butremains sufficiently viscous for the spinning of filaments and thecasting of films.

When the above examples are repeated using other alkyl phosphates, forexample, methyl phosphate and dipropyl phosphate the solutions obtainedare in general equivalent to the solutions of the examples.

As disclosed herein, alkyl phosphates are useful for dissolving any ofthe polymers of vinylidene cyanide including not only homopolymers butalso copolymers of vinylidene cyanide with materials copolymerizabletherewith such as styrene and substituted styrenes, vinyl esters,vinylidene monomers and the like. Also, the alkyl phosphate solvents ofthe present invention may be utilized in admixture with other solventssuch as acetone or methyl ethyl ketone, which in themselves are notsolvents for polymers of vinylidene cyanide, but which, together withalkyl phosphates in amounts as little as 20% by volume or even less formexcellent solvent mixtures. For example, a mixture of 60 volumes ofacetone and 40 volumes of triethyl phosphate readily dissolvesvinylidene cyanide polymers to form valuable spinning and castingsolutions.

Although specific examples of the invention have been described herein,it is not intended to limit the invention thereto, for numerousmodifications will be apparent to those skilled in the art and areincluded within the scope of the appended claims.

1. A solution of a polymer of vinylidene cyanide in a solvent comprisinga compound of the formula wherein R1 is an alkyl radical containing from1 to 3 carbon atoms and each of R2 and R3 is selected from the classconsisting of hydrogen and alkyl radicals containing from 1 to 3 carbonatoms.

2. A solution of a polymer of vinylidene cyanide, said polymerpossessing a molecular weight in excess of 25,000, in a compound of theformula Ra-O wherein R1 is an alkyl radical containing from 1 t0 3carbon atoms and R2 and R3 are selected from the class consisting ofhydrogen and alkyl radicals containing from 1 to 3 carbon atoms.

3. A solution suitable for the spinning of filaments and the casting offilms, said solution comprising from 8% to 20% by weight of a polymer ofvinylidene cyanide, said polymer possessing a molecular weight in excessof 25,000, dissolved in a compound of the formula R1O\ Rz-OP=O RaOwherein R1 is an alkyl radical containing from 1 to 3 carbon atoms, andR2 and R3 are selected,

' polymer of vinylidene cyanide possessing a molecular weight in excessof 25,000, dissolved in triethyl phosphate.

RICHARD F. SCHMIDT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,417,294 DAlelio Mar. 11, 19472,466,395 Dickey Apr. 5, 1949

1. A SOLUTION OF A POLYMER OF VINYLIDENE CYANIDE IN A SOLVENT COMPRISING A COMPOUND OF THE FORMULA 